Rick Riordan, the author, has stated that the original five books were always intended to be a complete story arc. However, there's always the possibility of future projects involving Percy Jackson and his friends.
Here's what we know:
* The *Heroes of Olympus* series is a direct sequel to *Percy Jackson and the Olympians*. This series continues the story of Percy and his friends, but with a new set of challenges and adventures.
* The *Trials of Apollo* series features Percy as a supporting character. While not a direct sequel, it does feature familiar faces from the *Percy Jackson* universe.
* The *Percy Jackson* Disney+ series is currently in production and will be an adaptation of the first book, *The Lightning Thief*. This could lead to future seasons adapting the rest of the series.
So, while a sixth book is not currently in the works, the *Percy Jackson* universe is far from over. There are still plenty of opportunities for Rick Riordan to continue the story of Percy and his friends, even if it's not in the form of a traditional sequel.